Punch press having magnetic reactive forces



J. RABINOW April 17, 1962 PUNCH PRESS HAVING MAGNETIC REACTIVE FORCESFiled May 12, 1960 Fla INVENTOR Jacob Rab/now ATTORNEY 3,d29,67iiPatented Apr. .17, 1962 3,029,676 PUNCH PRES HAVING MAGNETIC REACTIVEFORCE Jacob Rahinow, Taltoma Park, Md, assignor to Rahinow EngineeringCo., Inc., Rockville, Md. Filed May 12, 1960, Ser. No. 28,721 7 Claims.(Cl. 83-382) This invention relates to presses and more particularly topresses for large area Work pieces.

Deep throat presses, for instance punch presses, must be madestructurally heavy in order to withstand reactive press loading. Suchpresses in current industrial and commercial use have exceedingly heavyframes. As a result, they are expensive and comparatively difficult tomove.

An object of my invention is to make it possible to construct acomparatively lightweight punch press with a deep unobstructed throat.This is accomplished by the inclusion of means, preferably located inthe region of the tool holder of the punch press, for magneticallytransmitting reactive press forces between the upper and lower part ofthe throat. The effect is an electromagnetic clamp which preventsspreading of the throat.

Although the design of different manufacturers makes of presses variessomewhat, the frames of all presses, to my knowledge, are madesufiiciently strong to withstand press reactive forces within a givenparameter. My invention deviates from accepted design practices by usinga lightweight frame in place of the usual heavy casting, as the frame ofthe press. Essentially the only function of the top part of the frame ofmy press is to support and align the tool holder, and to serve as aportion of the means for establishing a favorable flux path between thebase of the frame and the upper part of the frame. These means may takethe form of an electromagnet and a highly permeable metal member.

Although the principles of the invention are very Well compatible with anumber of different types of presses such as for metal bending, metalpunching presses and others, the subsequent description deals only withpunch presses since such presses represent one preferred area of use ofthe invention. It is to be clearly understood that the illustrated formof the invention is given by way of example only.

Other objectives, features and advantages of this in vention will becomeevident in following the description of the illustrated form of theinvention.

FIGURE 1 is a diagrammatic side elevationalview of a press constructedin accordance with the invention.

FIGURE 2 is a diagrammatic front elevational view of the press in FIGURE1, the controls for the press being only schematically represented.

In the accompanying drawing, I have shown press 10 mounted on a suitablesupport such as table 12. Press 10 is intended to replace heavyindustrial presses or commercial presses which are ordinarily found inmachine shops, manufacturing plants, etc. However, the invention mayalso be applied to hobbiests presses or may take the form of anattachment for an ordinary, conventional press in order to increase thetolerable loading of the frame of the press.

Press frame 14 has a first, upper frame member 16 and a lower, secondframe member 18 joined together at their inner ends by frame member 20.The upper frame member 16 is in the form of a simple truss with abearing plate 22 at the outer end. Frame member 20 may be a post orsimply a U-shaped member (FIGURE 2) secured at its lower end to framemember 18 shown as a fiat bed plate. Frame 14 is essentially C-shapedwhen viewed from the side, and it has a deep throat 24 to receivecomparatively large area work pieces W.

Electromagnets 26 and 28 are secured to the frame members 16 and 18, andthey are spaced from each other to form a flux gap 3%. Tool holder 32 isconventional, and it is secured to the piston of a tool holder actuationcylinder 34 located between the two poles of electromagnet 26. Cylinder34 is secured to the bearing plate 22. Plate 36 is adjustably attachedto bearing plate 22 and the means for achieving this may vary. I haveillustrated two screws 38 and 49 in tapped openings in hearing plate 22and swivally connected to plate 36, however it will become at onceevident that the screws may be substituted by a single positioninghydraulic cylinder or a plurality of hydraulic cylinders, pneumaticcylinders, etc. where high speed operation is desirable.

The lower electromagnct 28 has two pole pieces directly opposing thepole pieces of electromagnet 26, and a flux return plate 42 whosefunction is similar to plate 36. The die or die holder 44 is disposedbetween the pole pieces of the lower electromagnet 28, and like toolholder 32, is conventional.

FIGURE 2 shows a conventional source 46 of fluid under pressure, forexample air or liquid, and a control valve 48 connected to source 46 byway of conduits 50. Valve 48 is a three-way valve, however the actualhydraulic circuit is not considered to be critical. Conduits 52 and 54extend from valve 48 to cylinder 34 in order to raise and lower the toolholder 32 in response to operation of valve 43. Switch 56 is connectedto a source of electrical potential and connected by wiring to the coilsof the electromagnet 26 and 28 respectively. There are meansinterlocking valve 48 and and switch 56 for simultaneous'operation, andthese means may be represented by a single lever 58 mounted on a pivotand pivotally connected to the valve and switch actuators. In the formsof my invention using one or more cylinders instead of screws 33 and 4%the additional cylinder or cylinders control valve assembly may also beinterlocked with lever 58 or may be separately controlled, as desired.Also, the force between magnets 26 and 28 may be used to punch workpiece W, in which case the cylinder 34 and its control 48 may be omittedin favor of a tool holder secured to plate 22 or the upper magnet.

Optimum flux path properties are established by the width of the gapbetween pole pieces of the electromagnets 26 and 28, the permeability ofthe metal thereof including plates 36 and 42, and the operating currentenergizing the coils. High magnetic attraction across the throat ofpress 10 is obtainable by using upper and lower electromagnets. In thoseinstances where the highest magnetic attraction is not necessary andwhere economy is important, two of the coils, for instance the coils ofelectromagnet 26, may be omitted so that the remaining cores and plate3d function as a flux return for electromagnet 28. Other variations arecontemplated by my invention. For instance, the invention may beembodied as an attachment composed of one or more electromagnetsattached to an otherwise conventional press across the throat thereofand this will have the effect of increasing the useful force capacity ofthe conventional press. Permanent magnets may, also, be employed withfiux shunting arrangements used to energize or reduce the flux in theworking gap as is done in magnetic clutches. These are well known andneed not be described here.

Other modifications as fall within the scope of the following claims,may be resorted to without departing from the protection afforded by theclaims.

I claim:

1. A press comprising a rigid frame having a rear enaaeve frame member,upper frame member stationarily fixed to said rear frame member, and alower frame member stationarily fixed to said rear frame member, saidframe being incapable of sufficiently and effectively resisting a givenreactive press force applied in a direction tending to spread said upperand lower members, said upper and lower frame members defining a deepthroat, tool actuat ing means reacting on said upper and lower framemembers to function on a work piece in said throat, and magnetic meansspaced from said rear frame member and operatively connected with saidupper and lower frame members and providing a reaction for said force toprevent spreading of said throat when said tool actuating means areoperative on a work piece and generate a force equal to said givenreactive press force.

2. The press of claim 1 and control means interlocked with said toolactuating means for energizing said magnetic means.

3. The press of claim 2 wherein said magnetic means include anelectromagnet, and means adjustabiy securing said electromagnet to oneof said frame members.

4. A punch press comprising a tool holder and operating device; a firstelectromagnet; a second electromagnet opposing said first electromagnet;said electromagnets having opposite poles facing each other and having aflux gap therebetween, the space between opposing poles forming a workpiece receiving station; means to energize said electromagnets; a baseagainst which said device reacts and to which said second electromagnetis secured; and rigid mechanical means against which said device reacts;said 'mechanical means being structurally incapable of resisting normalreactive press forces generated by said holder and operating devicewithout exceeding the elastic limit of said mechanical means orotherwise excessively spreading, to support said first electromagnet inopposing relation to said second electromagnet, whereby the magneticattraction between electromagnets transmits press frame or otherwisestructurally failing, and magnetic means spaced from said back memberand operatively connected with said upper and lower frame members buteaving said throat completely open and transmitting press forces betweentop and bottom of said throat to prevent said spreading under the samegiven maximum loading of said frame.

7. An attachment fora press to increase the useful working forceparameter of the press and wherein the press has a rigid frame providedwith fixedly connected frame members defining a throat, said attachmentcomprising electromagnetic means connected with said frame members'defining said throat for establishing a closed loop flux path acrosssaid throat to resist spreading the frame members under press loading bytransferring press forces between the frame members, and means tocontrol the energization of said electromagnetic means.

References Cited in the file of this patent UNITED STATES PATENTS

